1. Field of the Invention
This invention relates to multiple shot blasting systems. More particularly it relates to the timing of a blast and of individual shots constituting the blast.
2. Background Information
In the known systems of the aforementioned kind, the definition of the explosion times of all shots in the blast is obtained in two distinct steps. First, the time pattern of the shots within the blast is established by installing chosen delay arrangements connecting each shot timewise to a moment i.e. the firing moment. This moment is common to all shots in the blast, but remains initially undefined and so also the explosion times remain undefined.
The second step is the definition of the common firing moment e.g. by a push of a firing button on a firing box, thereby also defining the explosion times of all the shots in the blast.
This fundamental method has remained unchanged even though delay techniques have evolved from pyrotechnical delays to the latest programmable electronic delays, and interconnections between the charges and firing box, from firing cord to electrical wire and even in some cases a radio communication path between each charge and the firing box.
It is an object of the present invention to provide an alternative method of timing the shots in a blast and also apparatus for carrying out the said method.
A close concept of time is essential to the proper understanding of the present invention and in the following specification certain terms are used as follows:
Events occur at moments. The time of a moment is the coincident reading of a clock. A moment may therefore have different times at different clocks. Instead of the time of the moment of occurrence of an event, reference may also be made to the time of an event, meaning the same thing.
Real time is the clock reading of the common standard clock society uses to define the moments of its various events.
Two clocks are synchronized if from a reading of one of the clocks the coincident reading of the other clock can be calculated.
The act of synchronizing two clocks may consist of obtaining one pair of coincident readings and the ratio of the clock pulse repetition rates of the clock pulse generators of the two clocks, alternatively, of obtaining two pairs of coincident readings separated by a long enough time interval to provide the required accuracy of synchronism.
The term "blast" is used in this specification to denote a plurality of time-related explosions. Each individual explosion in the blast may also be referred to as a shot.
The "firing" of a charge, which may also be termed the "initiating" of a charge, denotes a human act which sets in motion a causally related chain of events which may include time delays and eventually leads to the explosion of the charge.
"Explosion" and "detonation" are used as synonyms.